Projector lampholder



Feb. 4, 1964 w. R. FRANCIS 3,120,417

PROJECTOR LAMPHOLDER Filed June 15, 1961 2 Sheets-Sheet 1 2s 4? fm enz'on 1449/[509/2? F 2"5/76/5,

b zi y 62,. y j Attorney.

Feb. 4, 1964 w. R. FRANCIS 3,120,417

PROJECTOR LAMPHOLDER Filed June 15, 1961 2 Sheets-Sheet 2 United States Patent 3,120,417 PROJECTOR LAMPHGLDER Wallace R. Francis, New Haven, Conn., assignor to General Electric Company, a corporation of New York Filed June 15, 1961, Ser. No. 117,222 Claims. (Cl. 339-93) This invention relates to an improved lampholder and in particular to an improved lampholder of the type utilized in projection apparatus.

In most, if not all, of the conventional picture projecting devices, an exciter lamp is mounted in a lampholder arranged in close quarters with its surrounding structure. The exciter lamp is essential to the operation of these devices, and to insure its continuous operation under adverse conditions, such as intermittent joggling and other various types of vibrations, it is important that the lamp be securely seated in the lampholder. To achieve such a result, prior art lampholders of the nature described have proved to be somewhat complicated in structure and as a consequence thereof, they are relatively expensive to manufacture. For such an application, it has therefore been found advantageous to provide a reliable and durable lampholder with an improved means for maintaining a secure complementary relationship between the lampholder and its supported lamp. It has also been deemed desirable to decrease the number of parts required for such a lampholder. This, of course, helps to reduce the cost of such a lampholder to the customer.

An important object of this invention is to provide an improved lampholder with a novel and low cost means for efliciently supporting a lamp.

It is another object of the present invention to provide an improved projector lampholder which is simplified, compact, and readily manufacturable.

It is a further object of the present invention to provide an improved projector lampholder having a one-piece base which efiiciently and securely supports and positions a projector lamp.

It is a still further object of this invention to provide an improved projector lampholder having a molded base member with an integral means for laterally and longitudinally positioning and securing a projector lamp in cooperative engagement therewith.

In carrying out my invention, in one form thereof, there is provided an improved lampholder for supporting a lamp of the type which includes a supporting portion with a guiding projecting and contact pins disposed on the bottom thereof. This lampholder comprises a one-piece insulating base and a plurality of contacts supported in the base for engagement with the contact pins of the lamp. The onepiece insulating base is molded to include a plurality of integral upright ears that project outwardly from a top surface of the base. These ears are disposed in juxtaposed relationship to adjacent outer surfaces of the supporting portion of the lamp when it is seated in the lampholder and efiiciently laterally position and brace the lamp securely therein. To provide an expeditious supporting seat for the guiding projection of the lamp within the lampholder, tapered ribs are formed on the inner wall of an aperture formed in the molded base. These ribs are disposed in such a manner as to provide a gradually increasing frictional engagement with the lamp projection while the lampholder is being seated. The one-piece base of the lamp-holder also includes integral supporting wings for readily fastening the lampholder to an appropriate supporting member. By means of the structure of the onepiece base of my improved lampholder, a novel and low cost means for supporting a lamp is thereby achieved.

Further aspects of my invention will become apparent hereinafter, and the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which I regard as my invention. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in conjunction with the accompanying drawings:

FIG. 1 is a perspective view of the improved lampholder embodying the present invention, with the lampholder being shown in supporting engagement with an appropriate projector lamp;

FIG. 2 is a perspective view of the improved lampholder, illustrating the positioning ears thereof;

FTG. 3 is a plan view of the improved lampholder;

FIG. 4 is a bottom view of the improved lampholder;

FIG. 5 is an enlarged fragmentary view of the central aperture of the lampholder shown in FIG. 3;'

FIG. 6 is a sectional view taken along the line 66 of FIG. 5, to illustrate the tapered configuration of the ribs of the central aperture;

FIG. 7 is a plan View of one arm of a slide projector wherein my improved lampholder may be expeditiously utilized, with part of the projector housing broken away to illustrate the interior thereof inclusive of the lampholder and the lamp;

FIG. 8 is a view taken generally along the line 8-8 of FIG. 7, partially broken away and partially in section, with the bottom portion of a projector lamp overlying the lampholder and spaced therefrom;

FIG. 9 is a sectional view of the lampholder, taken generally along the line 99 of FIG. 7, with the bottom portion of a mating projector lamp shown in the position wherein it is disposed after it has been forced outwardly from its seated position by an ejector lever FIG. 10 is a fragmentary view of the lampholder to show the configuration of the slots formed in the base for support and movement of the ejector member; and

FIG. 11 is a perspective view of the ejector member of the lampholder.

Referring first to FIG. 1 of the drawings, there is shown a projector exciter lamp 1 which includes a supporting portion or base 3. Base 3 of exciter lamp 1 is cylindrically configured and is adapted to be securely engaged by and positioned within my improved projector lampholder 5. The illustrated exciter lamp 1 is of a type generally employed in large numbers in the picture projection industry. This lamp 1 comprises an elongated and evacuated cylindrical envelope 7 having a hemispherically configured outer end 9. It will be understood that one or more suitable filament elements (not shown) are "arranged within envelope 7. As shown in FIGS. 8' and'9, the cylindrical bottom portion 11 of lamp 1 is encased by and aifixed to the lamp supporting base 3; To guide lamp 1 into'my improved lampholder 5 and also to'help support the lamp therein, a generally cylindrical projection 13 is formed on the bottom 15 of supporting base3. Projection 13 is centrally disposed and protrudes axially outwardly in perpendicular fashion from bottom 15. For electrically connecting the internal filament elements of the lamp to appropriate mating contacts of thdlampholder 5, male type pin contacts 17 have been provided. Pin contacts 17 project outwardly from bottom 15 of lamp base 3 to a lesser degree than projection 13 (as shown in FIGS. 8 and 9), being radially disposed from and in parallel relationship to the longitudinal axis of the lamp 1.

To enable my improved lampholder 5 to expeditiously seat exciter lamp 1 and also furnish a simplified means for readily fastening the lampholder to appropriate supporting structure, as shown in FIGS. 1-4, the unitary onepiece base member 19 has been provided. Base member 19 is of a molded insulating material such as one of the heat resistant phenolics, and it essentially includes a generally cylindrical body 21 (FIG. 2) with substantially parallel top and bottom walls 23 and 25, angularly spaced L-shaped positioning portions 27 and 29 (FIGS. 2 and 3), and supporting wings 31 which extend radially outwardly from outer surfaces 32 of positioning portions 29 (FIG. 9).

To provide the base member 19 with an integral seat for securely receiving and positioning the projector lamp 1, the L-shaped positioning portions 27 and 29 (FIG. 3) are arranged about the upper periphery of body 21 (FIG. 8), in oppositely disposed and angularly spaced pairs. For example, as shown in FIGS. 2 and 3, the positioning portions 27 are disposed on opposite sides of the longitudinal axis 34 of the lampholder and the positioning portions 29 are also disposed on opposite sides of the axis of the lampholder and spaced angularly approximately 90 from the positioning portions 27. Each of the positioning portions 27 and 29 includes a bottom section 33 (FIG. 3) which extends transversely to the axis of the lampholder and has a top surface coplanar to top wall 23. The top surface of section 33 (as illustrated in FIG. 8) helps to support bottom of lamp base 3 adjacent the outer rim of bottom 15. Each of the L-shaped portions 27 and 29 also includes a curved upright ear 35. Ears 35 project perpendicularly outwardly from the top surfaces of bottom sections 33 and have inner cylindrical surfaces 37 formed thereon. The cylindrical surfaces 37, as shown in FIG. 3, are molded as an integral part of base member 19 so that they are disposed in juxtaposed relationship to adjacent outer surfaces of the supporting portion 3 of the projector lamp 1 when the lamp is seated in the lampholder. (See FIG. 8.) Thus, when the lamp is seated, the cylindrical surfaces 37 of the ears 35 serve to grip or hug the adjacent cylindrical periphery of the lamp and laterally position it within the lampholder. By molding the upright ears 35 as an integral part of the lampholder base member 19, a rigid and inexpensive means is thereby achieved for laterally positioning and supporting the lamp within the lampholder.

To enable base member 19 of the lampholder 5 to be readily fastened to an appropriate supporting means, the aforementioned fastening wings 31, as shown in FIG. 8, are projected radially outwardly from the positioning portions 29. Wing 31 include apertures 39 for receiving screws 41. The screws 41 extend through apertures 39 of the wings and are threaded into engagement with tapped openings in supporting struts 43 of a projection apparatus 45 (FIG. 7). Projection apparatus 45 is a typical device wherein lampholder 5 may be expeditiously utilized, and it includes a relatively small box-shaped housing 46 wherein the lampholder 5 is supported. It will thus be seen by those skilled in the art that by means of the present invention, my improved base member 19 incorporates an integral means for securing the lampholder to its supporting structure.

To guide the cylindrical projection 13 of base portion 3 of the exciter lamp 1 into my improved lampholder 5, and at the same time provide a rigid integral supporting means for the cylindrical projection 13 of the lamp, as shown in FIGS. 3 and 4, base 19 has a generally cylindrical aperture or recess 47 formed therein. In the illustrated lampholder, aperture 47 is centrally disposed relative to lampholder axis 34 and opens into' top wall 23 and bottom wall 25 of the lampholder 5. The axis 34 of lampholder 5 is, of course, collinear with the longitudinal axis of lamp 1 when the lamp is seated. On the inner cylindrical wall of aperture 47, a plurality of angularly spaced parallel ribs 49 are formed. These ribs 49 are elongated and disposed radially from the axis 34 of the lampholder, being also V-shaped in cross section (FIG. 5) and tapered radially inwardly in depth between the top and bottom walls 23 and 25 (FIG. 6). Thus, the general periphery of aperture 47 at top wall 23 of base 19 (except for slot 53) is in the configuration of an uninterrupted circle (FIGS. 3 and 5), and the general periphery of aperture 47 at bottom wall 25 of the lampholder base (except for slot 53) is in the configuration of an interrupted circle having angularly spaced and inwardly pointed V-shaped projections (FIG. 4). The purpose and function of the tapered ribs 49 shall become apparent hereinafter.

When cylindrical projection 13 of the exciter lamp 1 is inserted into the central aperture 47 of lampholder 5, an enlarged longitudinally extending rib 51 (FIG. 9) which is formed on the outer surface of projection 13 must first enter elongated keyway slot 53 of aperture 47 (FIG. 5). Slot 53 extends longitudinally between the top and bottom walls of lampholder body 21 and assures the proper angular relationship between lamp 1 and lampholder 5 for mechanical and electrical engagement of the contacts. When lamp guiding projection 13 is properly aligned with and then inserted into lampholder aperture 47, projection 13 encounters an increasing frictional resistance as bottom 56 moves between top wall 23 and bottom wall 25 of the aperture. For example, when the bottom 56 of projection 13 first enters aperture 47 at top wall 23 of the lampholder, the cylindrical surface of projection 13 encounters a relatively smooth upper rim which has a slightly larger diameter than the principal diameter of projection 13. The lamp projection 13 thus readily enters aperture 47 upon the proper angular alignment of guiding rib 51. The lamp 1 is then, of course, pushed into the lampholder 5 and guided by movement of projection 13 within the aperture 47. As the lamp projection 13 rides downwardly through the aperture 47, as shown in FIG. 9, toward its seated position, it eventually becomes frictionally engaged by the innermost inclined edges 55 of tapered ribs 49. When central projection 13 of exciter lamp 1 has reached its seated position 13a (as shown in FIG. 9), the complementary relationship between the tapered ribs 49 of aperture 47 and the outer cylindrical wall of projection 13 is such that a press fit" is achieved. Bottom 56 of lamp projection 13 is then disposed underneath the bottom wall 25 of the aperture (as shown in FIG. 9), and appropriate portions of rib edges 55 are in secure gripping engagement with adjacent cylindrical surfaces of lamp projection 13.

It will now, therefore, be seen that by means of the tapered ribs 49 of lampholder recess 47, an etficient and integral means has been provided for expeditiously securing projection 13 of the exciter lamp 1 to my improved lampholder 5. Such a structural arrangement (i.e., the tapered ribs of lampholder aperture 47) readily lends itself to utilization with a projection apparatus wherein it is desirable that the lamp be readily insertable and removable, and rigidly positioned in a relatively small spatial area.

To furnish an appropriate means for electrically and mechanically engaging the pin contacts 17 of exciter lamp 1, as shown in FIGS. 3, 4, and 8, two female contacts 57 have been provided. Contacts 57 are of a type well known in the art, and they each include a pair of L-shaped fingers 59. The fingers 59 include upright portions 61 and outer or transverse ends 65. Portions 61 are inclined slightly toward each other so that they produce a tapered contact slot 63 having its maximum width at the bottom thereof (FIG. 8). The outer or transverse ends 65 of the fingers 59 extend in opposite directions from slot 63 and provide a pair of shoulders 67 which engage internal steps 69 of contact receiving recesses 71. On the bottom end 73 of each of the female contacts '57 (as shown in FIG. 8), there is provided a terminal blade portion with a detent hole therein for engagement with an associated quick connecting terminal. Between the bottom end 73 of each of the contacts 57 and the L-shaped fingers 59 thereof, a pair of laterally extending tabs 75 are formed. The tabs 75 are bent over, as shown in FIG. 4, to perpendicularly engage recessed bottom Wall surfaces 79 and thereby secure the contacts to the base member 19. An entrance for each of the female contacts 57 is provided by tapered surfaces 31 thereof. These tapered surfaces 81 are formed in the top of transverse ends 65 (viewing FIG. 8) and converge in wardly in a direction toward terminal blades 73 to facilitate the introduction of two contact pins 17 of the exciter lamp 1. Frusto-conical seats 82 (FIG. 3) are also molded on each side of recesses 71 at top wall 23 to help guide the pin contacts 17 into engagement with female contacts 57. To receive two other pin contacts 17, narrow slot 84a and circular slot 841) are also formed in top wall 23. Slot 84a extends radially and longitudinally and aids in preventing rotation of a seated lamp when it receives one of the pin contacts.

To enable one to readily remove the exciter lamp 1 from my improved lampholder 5, as shown in FIGS.

941, a pivoted ejector lever 83 has been provided. Lever 83 has a generally hook-shaped configuration and includes an integral arcuate bear-ing surface S5, connecting section 8 7, and arcuate force transmission section 89. The particular construction of lever -83 and its arrangement in lampholder 5 comprises the invention of Donald G. Kimball, and this construction and arrangement are described and claimed in his copending application Serial No. 117,330 filed concurrently herewith and assigned to the same assignee as the present invention.

To describe the structure of the lever 83 in greater detail, the bearing surface 85 thereof has a partially discshaped configuration. Between bearing surface 85 and the arcuate section 89, there is a generally L-shaped slot 91 (-FIG. ll). Upper surface 93 (viewing FIG. 9) of the connecting section 87 (FIG. 11) presents a flat outer edge which is relatively parallel to the top Wall 23 of insulating base member 19 when the exciter lamp 1 is seated in the lampholder 5. Actuating notch 95 is formed in upper surface 93. Notch 95 also includes a diagonal working surface 97 that serves as a camm-ing edge to allow clearance for an appropriate tool 99 into the bottom of not-ch 95.

The pivoted ejector lever -83 is mounted for rotation in the lampholder 5, as shown in FIG. 10, by radial slots 101, 103, and 105. Slots 101, 193, and 105 are formed in the top, side, and bottom walls, respectively, of base members 19. These slots are narrow in configuration and in coplanar relationship. Slot 101 is formed in the top and side walls of member 19, and provides an arcuate bearing surface 107 for pivotally supporting surface 85 of lever 83, and lip 1&9 for limiting downward movement of the lever. Slot 103 is formed in the side wall of member 19, and provides clearance for rotational movement of the lever 83 to its downward or actuated position. Slot 105 is formed in the bottom of base member 19, and it provides clearance for the rotational movement of stepped projection 111 formed on the inner arcuate surface of the lever.

Turning now to an explanation of the operation of ejector lever 83, attention is further directed to FIG. 9. When exciter lamp 1 is seated in lampholder 5, cylindrical projection 13 is in dotted position 13a and the actuating tip 112 is in its dotted position 112a. Upper surface 93 of lever 83 is generally parallel to the top wall '23 of the lampholder, as it is shown in dotted position 93a. With exciter lamp 1 in its seated position, the pivoted ejector lever 83 is forced into its dotted position, as shown in FIG. 9, by engagement of bottom 56 of lamp projection 13 with lever tip 112. A person who wishes to remove the exciter lamp from the la-mpholder then moves the shoulder of tool 99 downwardly into engagement with working surface 97 of actuating notch 95. Lover 83 thereupon pivots about its axis of rotation 113- to the position where it is shown in full in FIG. 9. During this move rnent, actuating tip 112 of the lever 83 engages the bottom of cylindrical projection 13 of the exciter lamp and propels it upwardly to the position where it is shown in full in FIG. 9. The lamp 1 may then be readily removed from the lampholder 5 by a simple pulling motion.

It will now, therefore, be seen by those skilled in the simplicity of the illustrated lampholder, it will be noted that it includes only four parts, the insulating base, the ejector member, and two contacts.

While in accordance with the patent statutes, I have described what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and -I, therefore, aim in the following claims to cover all such equivalent variations as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A lampholder for supporting a lamp of the type which includes a supporting portion with a cylindrical guiding projection and pin contacts extending therefrom, said lampholder comprising a one-piece insulating base of molded material, contact means cooperatively engaging said base and supported within said base for engagement with said pin contacts of said lamp, a plurality of integral upright ears projecting outwardly from said base, said ears being in juxtaposed relationship to adjacent outer surfaces of the supporting portion of the lamp when said lamp is seated in said lampholder thereby to laterally position and brace said lamp securely within said lampholder, a recess formed in said base for receiving said guiding projection, said recess having a generally cylindrical surface with tapered ribs projecting radially inwardly therefrom, said ribs being in parallel disposition to the longitudinal axis of the recess and deepest at the ends thereof farthest removed from said ears, thereby to provide gradually increasing frictional engagement with the cylindrical projection of the lamp upon the insertion of said lamp into said lampholder.

2. A lampholder for supporting a lamp of the type which includes a cylindrical supporting pontion with a cylindrical guiding projection and pin contacts extending therefrom, said lampholder comprising a one-piece insulating base of molded material, contact means cooperatively engaging said base and supported within said base for engagement with said pin contacts of said lamp, a plurality of integral upright ears projecting outwardly from said base, each of said ears having a cylindrical surface facing inwardly toward said lamp supporting portion when said lamp is seated in said lampholder, the cylindrical surfaces of said ears being in juxtaposed relationship to adjacent outer surfaces of the supporting portion of the lamp thereby to laterally position and brace said lamp securely within said lampho-lder, an aperture formed in said base for receiving said projection, said aperture having a generally cylindrical surface with tapered ribs projecting radially inwardly therefrom, said ribs being in parallel disposition to the longitudinal axis of the aperture and deepest at the ends thereof farthest removed from said ears, thereby to provide gradually increasing frictional engagement with the cylindrical projection of the lamp upon the insertion of said lamp into said lampholder.

3. A lampholder for supporting a lamp of the type which includes a cylindrical supporting portion with a guiding projection and pin contacts extending therefrom, said lampholder comprising a one-piece insulating base of molded material, said base having a longitudinal axis, a recess formed in said base for receiving said projection, contact means cooperatively engaging said base and supported within said base for engagement with said pin contacts of said lamp, a plurality of integral and arcuate up right ears projecting outwardly from said base, said ears being angularly spaced from each other and radially disposed from the longitudinal axis of the lampholder, each of said ears having a cylindrical surface facing inwardly toward said lamp supporting portion when said lamp is seated in said lampholder, the cylindrical surfaces of said ears being concentrically related to said lampholder axis and in juxtaposed relationship to adjacent outer surfaces of the supporting portion of the lamp thereby to laterally position and brace said lamp securely within said lampholder and a plurality of grooves formed in the periphery of said base, one of said grooves being located between each adjacent pair of said ears thereby to allow the flow of cooling air to said lamp when said lamp is seated in said lampholder.

4. A lampholder for supporting a lamp of the type which includes a supporting portion with a cylindrical guiding projection and pin contacts extending therefrom, said lampholder comprising a one-piece insulating base of molded material, said base having top and bottom walls and a longitudinal axis, contact means cooperatively engaging said base and supported within said base for engagement with said pin contacts of said lamp, a plurality of integral and arcuate upright ears projecting outwardly from said base, said ears being in juxtaposed relationship to adjacent outer surfaces of the supporting portion of the lamp when said lamp is seated in said lampholder thereby to laterally position and brace said lamp securely within said lampholder, integral flanges projecting transversely from at least two of said ears for fastening said lampholder to a supporting means, an aperture formed in said base for receiving said guiding projection, said aperture opening into said top and bottom walls of said base and having a generally cylindrical surface with tapered ribs projecting radially inwardly therefrom, said ribs being in parallel disposition to the longitudinal axis of the aperture and tapered so that they are deepest at the ends thereof adjacent the bottom Wall of the lampholder thereby to provide gradually increasing frictional engagement with the cylindrical projection of the lamp upon the insertion of said lamp into said lampholder.

5. A projector lampholder for supporting an exciter lamp of the type which includes a cylindrical supporting portion with a cylindrical guiding projection and pin contacts extending therefrom, said lampholder comprising a one-piece insulating base of molded material, said base having top and bottom walls and a longitudinal axis, contact means cooperatively engaging said base and supported within said base for engagement with said pin contacts of said lamp, a plurality of integral and arcuate upright ears projecting outwardly from said base, said ears being 'angularly spaced from each other and radially disposed from the longitudinal axis of the lampholder, each of said ears having a cylindrical surface facing inwardly toward the supporting portion of the lamp when said lamp is seated in said lampholder, the cylindrical surfaces of said ears being concentrically related to said lampholder axis and in juxtaposed relationship to adjacent outer surfaces of the Supporting portion of the lamp thereby to laterally position and brace said lamp securely within said lampholder, integral flanges projecting transversely from at least two of said ears for fastening said lampholder to a supporting means, an aperture formed in said base for receiving said guiding projection, said aperture opening into said top and bottom walls of said base and having a generally cylindrical surface with tapered ribs projecting radially inwardly therefrom, said ribs being in parallel disposition to the longitudinal axis of the aperture and tapered so that they are deepest at the ends thereof adjacent the bottom wall of the lampholder thereby to provide gradually increasing frictional engagement with the cylindrical projection of the lamp upon the insertion of said lamp into said lampholder.

References Cited in the file of this patent UNITED STATES PATENTS 2,659,061 Mirabella Nov. 10, 1953 2,894,240- Mautner July 7, 1959 3,018,462 Barre et al. Jan. 23, 1962 FOREIGN PATENTS 995,648 France Aug. 22, 1951 676,861 Great Britain Aug. 6, 1952 

1. A LAMPHOLDER FOR SUPPORTING A LAMP OF THE TYPE WHICH INCLUDES A SUPPORTING PORTION WITH A CYLINDRICAL GUIDING PROJECTION AND PIN CONTACTS EXTENDING THEREFROM, SAID LAMPHOLDER COMPRISING A ONE-PIECE INSULATING BASE OF MOLDED MATERIAL, CONTACT MEANS COOPERATIVELY ENGAGING SAID BASE AND SUPPORTED WITHIN SAID BASE FOR ENGAGEMENT WITH SAID PIN CONTACTS OF SAID LAMP, A PLURALITY OF INTEGRAL UPRIGHT EARS PROJECTING OUTWARDLY FROM SAID BASE, SAID EARS BEING IN JUXTAPOSED RELATIONSHIP TO ADJACENT OUTER SURFACES OF THE SUPPORTING PORTION OF THE LAMP WHEN SAID LAMP IS SEATED IN SAID LAMPHOLDER THEREBY TO LATERALLY POSITION AND BRACE SAID LAMP SECURELY WITHIN SAID LAMPHOLDER, A RECESS FORMED IN SAID BASE FOR RECEIVING SAID GUIDING PROJECTION, SAID RECESS HAVING A GENERALLY CYLINDRICAL SURFACE WITH TAPED RIBS PROJECTING RADIALLY INWARDLY THEREFROM SAID RIBS BEING IN PARALLEL DISPOSITION TO THE LONGITUDINAL AXIS OF THE RECESS AND DEEPEST AT THE ENDS THEREOF FARTHEST REMOVED FROM SAID EARS, THEREBY TO PROVIDED GRADUALLY INCREASING FRICTIONAL ENGAGEMENT WITH THE CYLINDRICAL PROJECTION OF THE LAMP UPON THE INSERTION OF SAID LAMP INTO SAID LAMPHOLDER. 